================
@@ -1204,21 +1230,30 @@ CIRABIRewriteContext::rewriteCallSite(mlir::Operation
*callOp,
dl);
newArgs.push_back(arg);
} else if (ac.kind == ArgKind::Indirect) {
- // byval and byref: allocate a stack slot, copy the value in, and pass
- // the pointer. The alloca+store pattern is identical for both; the
- // attribute distinction (llvm.byval vs llvm.byref) is applied by
- // updateArgAttrs. byref does not receive llvm.noalias or llvm.noundef
- // because it does not assert exclusive ownership of the storage.
- mlir::Type argTy = arg.getType();
- auto ptrTy = cir::PointerType::get(argTy);
- uint64_t align = ac.indirectAlign.value();
- StringRef slotName = ac.byVal ? "byval" : "byref";
- auto slot = cir::AllocaOp::create(builder, call.getLoc(), ptrTy,
- builder.getStringAttr(slotName),
- builder.getI64IntegerAttr(align));
+ // byval hands the callee its own copy. byref must name the caller's
+ // storage instead: CIRGen materializes the argument into a temporary it
+ // destroys after the call and emits the operand's load immediately
+ // before that call, so forwarding the alloca hands the callee the object
+ // the caller destroys, with nothing able to write it in between.
+ if (!ac.byVal) {
+ WholeRecordSource src = getWholeRecordSource(arg);
----------------
erichkeane wrote:
```suggestion
auto [alloca, load] = getWholeRecordSource(arg);
```
https://github.com/llvm/llvm-project/pull/216499
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